Various types of nephelometers exist. One of the best known nephelometers is a type sold commercially by Meterological Research Inc. See U.S. Pat. No. 3,563,661 by Robert J. Charlson, et al., issued Feb. 16, 1971 and U.S. Pat. No. 3,953,127 by Norman C. Ahlquist, et al. issued Apr. 27, 1976 for detailed description and operation. Instruments produced according to these disclosures suffer from truncation errors which make them unsuitable for use in marine atmospheres where large aerosol particles often cause deterioration of the atmosphere's optical quality and exacerbate the truncation error. U.S. Pat. Nos. 3,563,661 and 3,953,127 each disclose a cosine light source and a collimated sensor. U.S. Pat. No. 3,563,661 provides an integrating nephelometer having a housing for containing a sample volume of the atmosphere and a light pulse for illuminating a portion of the sample. One detector receives scattered light from the light pulse and provides an electrical output signal in response thereto. Another detector receives light directly from the light source and provides an electrical output signal defining a reference signal caused by light pulse intensity. These two output signals are compared for an indication of light scattered by aerosol particles in the sample.